1. Field of the Disclosure
The present disclosure relates to a method of checking the state of how an earphone equipped with a 3-axis acceleration sensor is being worn by a user, and to an audio playback apparatus that uses such an earphone.
2. Description of Related Art
Typically, headphones are used as an apparatus for the purpose of a user converting an audio signal output from an audio playback apparatus into a sound wave (audible sound), basically to listen to music or other such audio alone. The headphones in this specification are connected to such an audio playback apparatus in a wired or wireless manner, and include monaural types which use a single earphone, and stereo types provided with a pair of left and right earphones. An earphone herein refers to the component of headphones worn so as to bring a speaker close to one of the user's ears.
Hitherto, technology providing audio-based navigation to pedestrians wearing headphones has been proposed (see Japanese Unexamined Patent Application Publication No. 2002-5675). With this technology, the angle of cranial rotation with respect to the direction in which a user is traveling (the front-to-back direction of the user's body) is computed as follows. Namely, established laser range-finding methods are used to detect the shortest distance from the user's left shoulder to the left side of the headphones, and also to detect the shortest distance from the user's right shoulder to the right side of the headphones. Additionally, a sensor worn near the base of the head is used to detect the direction of cranial rotation (right-handed turning or left-handed turning as viewed from above). The angle of cranial rotation with respect to the user's travel direction is computed on the basis of these two shortest distances and the direction of cranial rotation thus detected. The position of the sound source is corrected on the basis of the angle of cranial rotation.